Modbus master-slave station explanation

In a Modbus communication system, we can consider the master as an instructor, while the slave is like a soldier.

Imagine in military training, the instructor (master station) is responsible for commanding the training, and he will tell the soldiers (slave stations) when to start and when to stop. Each soldier has a unique name (in the Modbus system, this is equivalent to the ID or address of the slave station) to enable the instructor to command them accurately.

For example, an instructor may say to a soldier, "Xiaoming, go do 50 push ups!" or "Xiaohua, report your current state.

In the Modbus system, the master station sends requests to specific slave stations (like an instructor calling out a soldier's name) to obtain information or command them to perform specific actions.

A more professional explanation is that Modbus communication system is a master-slave system. The master station (also known as the controller) initiates communication by sending requests to the slave stations (also known as devices or sensors) to perform certain operations or return certain information. Each slave station has a unique address so that the master station can accurately point to it. In a Modbus communication system, there is only one master station, but there can be multiple slave stations.